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Dislocation loops in NiCo and NiFe, both being single-phase, equimolar solid solution alloys, are generated by in situ high-voltage electron irradiation and characterized inside a transmission electron microscope. In addition to the different defect growth rates, the two alloys present dislocation loops with distinct shape evolution and element segregation, which reflect the element-sensitive, intrinsic properties (e.g., defect energetics, lattice distortion, and local ordering) of the alloys. These results provide evidence that the structure and dynamics of radiation-induced defects in concentrated alloys depend on not only the number but also the species of alloying elements. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Using ion irradiation and transmission electron microscopy, temperature dependent void swelling and dislocation loop evolution in equiatomic NiCoFeCrMn and NiCoFeCrPd high entropy alloys were investigated. Voids were observed in all tested conditions. An order higher of swelling was observed in both HEAs as temperature increased from 420 to 580 °C. Alloying with Pd was found to have a stronger suppression effect on void and dislocation loop growth than alloying with Mn. Possible contributions to the swelling resistance were explored, including localized lattice distortion and higher defect migration barrier in NiCoFeCrPd. Additionally, no phase decomposition was observed in either alloy. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

The evolution of irradiation-induced atomic strain in an equiatomic NiFe concentrated solid-solution alloy is investigated using both atomistic simulations and x-ray diffraction analysis. The irradiations are performed using 1.5 MeV Ni ions to fluences ranging from 1 × 10 13 to 1 × 10 14 cm − 2 . The irradiation simulations are carried out by overlapping 5 keV Ni recoils cascades up to a total of 300 recoils. An increase of volumetric strain is observed at low dose, which is associated with production of point defects and small clusters. Relaxation of strain occurs at higher doses, when large defect clusters, e.g., dislocation loops, dominate. [ABSTRACT FROM AUTHOR]

Defect production and growth in CrFeCoNi, a single-phase concentrated solid solution alloy, is characterized using in situ electron irradiation inside a transmission electron microscope operated at 400–1250 kV and 400 °C. All observed defects are interstitial-type, either elliptical Frank loops or polygonal (mostly rhombus) perfect loops. Both forms of loops in CrFeCoNi exhibit a sublinear power law of growth that is > 40 times slower than the linear defect growth in pure Ni. This result shows how compositional complexity impacts the production of Frenkel pairs and the agglomeration of interstitials into loops, and, thus, enhances the radiation tolerance. [ABSTRACT FROM AUTHOR]

We perform molecular dynamics simulations of Ni ion cascades in Ni and equiatomic NiFe under the following conditions: (a) classical molecular dynamics (MD) simulations without consideration of electronic energy loss, (b) classical MD simulations with the electronic stopping included, and (c) using the coupled two-temperature MD (2T-MD) model that incorporates both the electronic stopping and the electron-phonon interactions. Our results indicate that the electronic effects are more profound in the higher energy cascades and that the 2T-MD model results in a smaller amount of surviving damage and smaller defect clusters, while less damage is produced in NiFe than in Ni. [ABSTRACT FROM AUTHOR]

Using molecular dynamics simulations, the formation and growth of stacking fault tetrahedra (SFT) are captured by vacancy cluster diffusion and aggregation mechanisms in Ni. The vacancy-tetrahedron acts as a nucleation point for SFT formation. Simulations show that perfect SFT can grow to the next size perfect SFT via a vacancy aggregation mechanism. The stopping and range of ions in matter (SRIM) calculations and transmission electron microscopy (TEM) observations reveal that SFT can form farther away from the initial cascade-event locations, indicating the operation of diffusion-based vacancy-aggregation mechanism. [ABSTRACT FROM AUTHOR]

• The creep resistance is the highest in CoCrNi, followed by CoCrFeMnNi and then CoCrFeN alloys, while the Monkman-Grant relationship gives similar failure strain. • While the room and cryogenic temperature strength is governed by solid solution effects, the contrast of creep behavior in these subset alloys is primarily governed by the stacking fault energy. • The best performing CoCrNi has comparable creep resistance as commonly used precipitate/martensite-strengthened ferritic alloys. Long-term tensile creep experiments were performed at 973 K on a family of multicomponent equiatomic solid solution alloys with face-centered cubic crystal structures, including quinary CoCrFeMnNi alloy and quaternary CoCrFeNi alloy, together with our previous report on ternary CoCrNi alloy. Analyzing the steady-state and transient creep properties and characterizing the precipitate evolution, it is suggested that dislocation creep be the dominant deformation mechanism for all these alloys. Although CoCrNi shows the highest room-temperature strength and the lowest creep rate at 973 K, the creep lifetime data for all three alloys are similar and can be described by the Monkman-Grant relationship. [Display omitted] [ABSTRACT FROM AUTHOR]

We systematically explored the indentation size effect (ISE), which is not expected to occur in non-crystalline materials due to the absence of dislocations and strain hardening, in bulk metallic glass (BMG). A series of nanoindentation experiments with different indenters result in somewhat surprising observations that show that ISE clearly does exist in BMG and can even be described by the ISE model for crystalline materials. The results are discussed in terms of possible mechanisms responsible for the ISE in BMG. [Copyright &y& Elsevier]